Ammonia has been used in several different types of foodstuff treatments. For example, U.S. Pat. No. 3,023,109 to Hines shows treating fresh red meat products with ammonia gas to improve the red color of the uncooked meat. Inventor's certificate SU528923 to Smol' skii et al. discloses a process in which the ammonia gas or aqueous ammonia is applied to fresh meat products to help improve the storage life of the uncooked meat products at temperatures above freezing. Japanese patent No. Sho 64-39965 by Nakayama discloses that gaseous or aqueous ammonia may be used to remove undesirable odors from fresh fowl meat. Ammonia is also known to provide an antimicrobial effect in meat products as indicated in U.S. Pat. No. 5,871,795 to Roth. Ammonia has also been used to treat other types of foodstuffs as shown in U.S. Pat. No. 5,082,679 to Chapman. The Chapman patent shows a process which uses ammonia to detoxify grains that have been contaminated with aflatoxin.
Although ammonia-based treatment materials (such as gaseous and aqueous ammonia) and other treatment materials are known to provide beneficial effects in foodstuffs, there are problems associated with treating foodstuffs with such materials. One problem associated with the application of ammonia-based treatment materials to meat products is that ammonia can change the texture of the meat. Another problem is that ammonia-based material treatments can leave an undesirable ammonia odor in the meat product. U.S. Pat. No. 5,871,795 to Roth discloses a treatment process in which a relatively high ammonia gas pressure is used to reduce the treatment times and thereby avoid imparting an ammonia odor to the treated meat and avoid undesirable changes in the texture of the treated meat while still providing a desirable antibacterial effect. U.S. Pat. No. 6,142,067 to Roth discloses a system in which problems from ammonia treatments for highly comminuted meat are avoided by sparging the ammonia-based treatment fluid into a stream of comminuted meat product and then further comminuting the meat product. This sparging and comminuting arrangement has been shown to better distribute the ammonia treatment material in the meat product and to avoid leaving an ammonia odor in the meat. U.S. Pat. Nos. 7,093,973 and 7,322,284 to Roth show other types of sparging devices for applying ammonia-based treatment material and other pH modifying materials to a stream of highly comminuted foodstuff. U.S. Pat. No. 6,713,108 to Roth discloses a treatment process in which meat products are exposed to ammonia gas and a mechanical action is then applied to avoid producing an ammonia odor in the treated meat product. For larger cuts of meat, U.S. Pat. No. 6,387,426 to Roth discloses applying an ammonia-based treatment material to the surface of a meat product and then employing pressure in a controlled environment to drive the treatment material in to the meat product without over treating.
The above-described prior art processes for applying an ammonia-based treatment material to foodstuffs generally employ two techniques to address the problem of ammonia odor in the treated product. One technique is to limit the time of contact between the foodstuff and the treatment material. The other technique is to apply mechanical action to drive the ammonia-based treatment material into the foodstuff so that the treatment material is bound within the foodstuff. Although these techniques are effective for some applications, they are limited to relatively low concentrations of ammonia in the treatment material. It may be desirable, however, to apply relatively concentrated ammonia-based treatment materials to foodstuffs in order to obtain an enhanced antimicrobial effect. For example, for foodstuffs such as meat products which are injected with brines, it is desirable to eliminate live bacteria at the product surface prior to brine injection in order to reduce the risk of inadvertently carrying surface bacteria into the interior of the meat product with the injection needles. It is also generally desirable to eliminate live bacteria at the surface of a foodstuff that will undergo grinding or further comminuting steps in order to prevent the microbes at the surface of the foodstuff from being spread to other points in the foodstuff in the course of the grinding or further comminuting steps. Although the prior art suggests that ammonia-based treatment materials may be effective for reducing live bacteria counts at the surface of a foodstuff, the problems of excessive ammonia absorption and ammonia odor in the treated product have been limiting factors in the use of ammonia-based treatment materials.